Tread-belt link and cooperating driving tumbler



1955 T. o. DAVIDSON ETAL 2,

TREAD-BELT LINK AND COOPERATING DRIVING TUMBLER Filed June so, 1952 3 4 Sheets-Sheet 1 zevorz o. DAVIDSON TOM LEAQMONT INVENTORS waf- FIG-(4 y 7 1955 T- o. DAVlDSON ETAL 2,72

TREAD-BELT LINK AND COOPERATING DRIVING TUMBLER Filed June 30, 1952 4 Sheets-Sheet 2 TREVOIZ O. DAVIDSON TOM LE'AIZMONT INVENTORS A TTOIZNZ;

FIG- 6 Dec. 20, 1955 'r. o. DAVIDSON ET AL 2,727,794

TREAD-BELT LINK AND COOPERATING DRIVING TUMBLER Filed June 50, 1952 4 Sheets-Sheet 3 TRE'VCQ O. DAVIDSON TOM LEFUZMONT INVENTOR.

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HTTCENE syl 1955 T. o. DAVIDSON ET AL 2,727,794

TREAD-BELT LINK AND COOPERATING DRIVING TUMBLER Filed June 30, 1952 4 Sheets-Sheet 4 FIGLIO WM m lTN vmm m 0 N A Q& OL V M Tm BY 4 (u/ United States Patent TREAD-BELT LINK AND COOPERATING DRIVING TUMBLER Trevor 0. Davidson and Tom Learmont, Milwaukee, Wis., assignors to Bucyrus-Erie Company, South Miiwankee, Wis., a corporation of Delaware Application June 30, 1952, Serial No. 296,446

12 Claims. (Cl. 305-) This invention relates to new and useful improvements in endless tread-belt links and cooperating driving tumblers, and more particularly to such links and tumblers as are used on heavy mobile machinery such as power excavators.

This invention is a further improvement of the link and driving tumbler shown and described in U. S. Patent No. 2,530,379, issued to Trevor 0. Davidson, November 21, 1950.

In tread-belt links of the general type described herein, the pitch angle of a link is the angle at the center of the tumbler that is subtended by a line drawn from one pivot-pin connection to the other pivot-pin connection of the link. The pitch angle of the tumbler is the angle at the center of the tumbler subtended by a line drawn from the center of one tumbler lug to the center of an adjoining tumbler lug. The difference between the two angles is known as pitch angle error. When the pitch angle of the tumbler is greater than the pitch angle of the link, the difference between the two angles is referred to as positive pitch angle error. pitch angle of the link is greater than the pitch angle of the tumbler, the difference between the two angles is referred to as negative pitch angle error.

Wear of the mechanism causes the pitch angle of the link to increase, and the pitch angle of-the tumbler to decrease. The presence of stones or dirt obstructions between the link and tumbler surfaces may force the link away from the tumbler, thus causing the angle of pitch of the link to decrease.

Beyond defined limits, either a positive or negative pitch angle error will cause interference between tumbler and link, and this, in turn, results in the tread-belt either jamming or breaking. Error within these limits is referred to as allowable pitch angle error.

Accordingly, it is the principal object of this invention to redesign and improve former links, so that:

(l) The allowable pitch angle error will be increased.

(2) The rate of change of angle of pitch error will be diminished.

Interference may develop even though the mechanism is working within an allowable pitch angle error, when stones or dirt obstructions are lodged between thedriving surfaces of the tumbler driving lugs and the link driving flanges. Interference of this nature will likewise cause jamming or breaking of the tread-belt.

Accordingly, it is another principal object of this invention to redesign and improve former links so that a greater accumulation of stones or dirt obstructions lodged between the respective driving surfaces of tumbler and link may be accommodated without interference.

As a link having longitudinally staggered driving flanges engages or disengages the tumbler, wear upon the respective driving surfaces of the mechanism is uneven if driving is designed for two or more simultaneously-striking driving surfaces on the link. A link so designed will not function efliciently because the uneven wear will cause one driving surface to take the driving force supplied by Similarly, when the i the tumbler, while the other driving surface, although designed to take an equal load, takes little or none at all. This, in turn, results in the link wearing out prematurely.

Accordingly, it is a third principal object of this invention, to so design the driving surfaces of the link, and their respective cooperating tumbler driving surfaces, that this uneven Wear, caused at the moment of engagement or disengagement, is substantially eliminated.

This invention consists in the novel parts, and in the combination and arrangement thereof, which are defined in the appended claims, and of which one embodiment is exemplified in the accompanying drawings, which are hereinafter particularly described and explained.

Throughout the description, the same reference number is applied to the same memberor similar members.

Referring now to the accompanying drawings, it will be seen that:

Figure l is a plan view of the link.

Figure 2 is a half-sectional elevation of the link, taken along the line 2-2 of Figure l.

Figure 3 is a sectional elevation of the link, taken along the line 3-3 of Figure 1.

Figure 4 is an end view of the link, taken along the line 4-4 of Figure 1.

Figure 5 is a partial side elevation of the driving tumbler in driving engagement with a link. Phantom lines, represented by a series of dots and dashes, show portions of adjoining links swung into the same horizontal plane as that of the driven link.

Figure 6 is a plan view taken along the line 6-6 of Figure 5, and shows the method of connecting successive links together.

Figure 7 is a side elevation of the driving tumbler, showing it in normal forward driving engagement with the links comprising the endless tread belt.

Figure 7A is a partial side elevation of the driving tumbler and a link as it engages the tumbler when the tumbler acts as a brake on the tread-belt as the machine moves downhill. I

Figure 8 is a partial section taken along the line 88 of Figure 6.

Figure 9 is a partial section taken along the line 9-9 of Figure 5.

Figure 10 is a side elevation of the complete endless traction unit.

The direction of travel of the links will hereinafter be called longitudinal, and the direction perpendicular thereto (i. e., across the link from side to side) will be called lateral.

Referring now to Figure 1, it is seen that the link, is laterally (i. e., across the sheet) wide, and is longitudiv nally (i. e., up and down on the sheet) relatively narrow.

The bottom of the link affords a ground-engaging surface 20 (Figures 2 to 4). On the top of the link are two longitudinally-staggered laterally-spaced driving flanges 21, which laterally bound a central longitudinal wheelreceiving channel 22.

Each link is pin connected by the following described means to its adjacent linksto form the tread-belt. On each laterally extended edge of the link there are a series of ears 23 to 27 inclusive defining a series of recesses 28 to 32 respectively which are adapted to receive the ears of adjoining links. Bars 23 to "27 contain transverse holes 33 for receiving pivot pins 34 and 35 which are inserted inwardly from each side of the link and are held in placeby holding pins 36.

The lateral edges of each flange 21 consist of longitudinally upwardly inclined lateral driving surfaces 21:: and 21b respectively adapted to be driven by the tumbler as hereinafter described. The slope of the outer driving surface 21a of each flange is greater than the slope of the inner driving surface 21b,'both slopes being so chosen that a line perpendicular to each surface at the point of driving contact with the driving lug of the tumbler will pass through the body of the link adjacent to and approximately thesame distance inwardly of the opposite pivot-pin axis of the link.

Longitudinally aligned with each flange 21 is a tumbler bearing surface 37 which extends longitudinally from the inner lateral edge of the flange for approximately onehalf of its length on the body of the link and thence for the remainder of its length on an ear 24 of the link. It will be noted that the bearing surface 37 of each link is symmetrically disposed about its vertical axis A (see Figure 1). Furthermore, it is seen that, by virtue of the longitudinally staggered arrangement of the flanges 21, an elongated bearing surface aligned with each flange is obtained, and a major portion of such surface, as well as the stress point at the angle formed by the flange and such surface, is located on the body of the link rather than on or adjacent the weaker car 24. Other operating advantages of this elongated bearing surface are described hereinafter.

Turning now to Figure 7, it is seen that 39 is the driving tumbler of the invention, and that on the side faces of this tumbler there are disposed a succession of peripherally-spaced laterally-projecting driving lugs for making driving contact with the flanges 21 of the tread-belt links.

For convenience, the tumbler driving lugs shown on the near face of the tumbler in Figures 5 to 7 are designated by reference numbers to 47 inclusive, and those on the far face of the tumbler by reference numbers 40' to 46 inclusive. Similarly the links shown in Figure 7 about the periphery of the tumbler are designated by reference numbers to 56 inclusive and the near-side driving flanges on the links are designated by the reference number 21 and the far-side driving flanges by reference number 21'. Similarly, the numbers representing driving surfaces of the far-side links and lugs in Figures 5 to 7 are primed.

The central peripheral surface 60 of the tumbler is designed to have bearing contact with the central channel 22 of the link.

Each driving lug of the tumbler has a peripheral bearing surface 61 which is designed to have bearing contact with the bearing surface 37 of a link. Bearing surfaces 37 of the links are preferably so inclined and curved in a longitudinal direction as to be perpendicular to the radius of the tumbler and have a radius of curvature equal to that of tumbler-bearing surfaces 61.

Each lug also has longitudinally inclined lateral driving surfaces 62:: and 62b which are designed to have driving contact with the driving surfaces 21a and 21b respectively of the link driving flanges 21. The slope of the inner inclined surface 62a of the lugs is greater than the outer slope 62b, and both slopes are so chosen that, when one of the driving surfaces 62a or 62b of a Iug isin driving contact with a flange of the link, the line of driving force generated'by the lug upon the link flange perpendicular to said one of the driving surfaces of the lug, at the point of driving contact between the lug and the flange, passes through the body of the link adjacent to and inwardly of the axis of the opposite pivot connection of the link to its adjoining link.

The tumbler is so constructed that, when the treadbelt is assembled with the tumbler, and the tumbler rotates clockwise as shown (see Figure 7), only the driving flanges 21 and 21' of link 52 are in full striking, driving contact with the driving lugs 42' and 43 of the tumbler. The flanges 21 and 21' of link 51 are shown in the process of breaking contact with tumbler driving lugs 41' and 42, and the flanges of links 53, 54, and 56 are .shownto be not yet in driving contact with the driving lugs of the tumbler. When however, the bearing surfaces of the links andthe tumbler become worn, sothat the pitch-angle error of the links approaches zero,

the gap between the driving surfaces 21a and 62a of the near-side flanges of links 53, 54, 55 and 56 and near-side driving lugs 44, 45 and 46 will decrease, and these links will shift counterclockwise relative to the tumbler, so that eventually interference will occur between near-side flange 21 of link 56 and lug 47 of the tumbler, rendering the tread-belt useless. Similarly when pitch-angle error increases beyond the allowable limit due to wear, the gap between the driving surfaces 62b of the far-side flanges of links 53, S4, 55 and 56 and far-side driving lugs 43, 44' and 45' will decrease, so that eventually interference will occur between far-side flange 21 of link 56 and lug 46 of the tumbler.

By making possible a much longer bearing surface between the links and tumbler, than in conventional tread-belts, the invention reduces wear that causes such intleiference, and thereby lengthens the life of the tread- Another featureof this invention is that, when a lug of the tumbler is in driving contact with edge 21a or edge 21a of a link flange, substantially all of the peripheral bearing surface of the lug is in contact with the tumbler bearing surface associated with the flange of the succeeding link. This increases the working bearing surfaces, and thereby decreases wear. and the chance of the above- Idefcribed interference, and increases the life of the tread- Another feature of this invention, shown in Figure 7, is that, in addition to the elongated bearing surfaces 37 making it possible to provide increased bearing contact between the tumbler driving lugs and the bearing surfaces of the links, the elongated bearing surfaces 37 also make it possible to avoid another type of interference between the tumbler lugs and link flanges by providing a-relatively large space between the rear inclined tumbler driving surfaces (62b and 62a for clockwise rotation, or 62 and 62b for counterclockwise rotation) and the forward inclined driving surfaces (21b and 21a for clockwise rotation or 21a and 21b for counterclockwise rotation) of the driving flanges. This prevents interference by providing a shifting space for the driving flanges when a stone or dirt lodges between a link andthe tumbler causing one or more links to shift peripherally with respect to the tumbler. Thus, if a stone lodges between the periphery of the tumbler and the bottom of the channel of link 52 (see Figure 7), this link will be forced away from the tumbler, thereby drawing link 53 upwardly. The near driving flange 21 of link 53 will then shift clockwise closer to tumbler lug 43 and the far driving flange 21' of link 52 will approach tumblerlug 42. This will in turn cause the driving flanges 21 and 21' of link 54 to approach tumbler lugs 44 and 43', because the upward movement of link 53 draws link54 clockwise around the tumbler. Similar shifting of the links about the periphery of the tumbler could be caused by a stone lodged between say, driving flange 21 of link.52 and lug 43 of the tumbler. In either event, if the aforementioned space between the tumbler lugs andulink flanges did not permit this shifting of the links about the tumbler, either jamming or breakage of the tread-beltwould result from the interference of the tumbler lugs and link flanges. In general, the greater the space-between the lugs and the flanges, the greater can be the size of the stone or other obstruction between the tumbler and the links without developing interference. Inthis invention, a materially-larger space is made possible by virtue'of the elongated bearing surfaces 37 of the links.

Another advantage of the elongated bearing surface 37 is that substantially all of the peripheral bearing surface of the tumbler lugs is in bearing contact withthe tumblerbearing surface 37 that is longitudinally aligned with saidlugandassociated with the flange of the link that succeeds the link with which the driving flange is in driving contact. Thus, inFigure 7, lugs 42 to 45 inclusive are seen to be in full bearing contact with surfaces 37 of links 52 to 55 inclusive. When rotation of the tumbler is reversed from the direction shown in Figure 7, the same phenomenon is observed with reference to the far-side lugs, flanges and bearing surfaces.

Another feature of the invention is that, in order to achieve ease .of entry and proper meshing of the link flanges and tumbler lugs, the inner driving surfaces 21b of the link driving flanges are curved so that they are convex (see Figure 4), the radius of this curvature of this inner driving surface being less than the radius of curvature of the outer driving surfaces 21a, which for ease of casting are usually made and are shown herein to be nearly straight.

Turning now to Figure 7A, this shows the relative position of the driving flanges 21 and 21 and cooperating tumbler lugs when the machine is moving downgrade (rotation of the tumbler being clockwise as in Figure 7). In this situation, the tread-belt has a tendency to overrun the rotating tumbler, and the tumbler lugs have a braking effect instead of a driving elfect on the treadbelt. The link shown in Figure 7A is starting to engage the tumbler. Surfaces 21b and 21a of driving flanges 21 and 21 respectively are in contact with cooperating tumbler lugs 48 and 48 respectively. The lines of force F and F of lugs 48 and 48 on flanges 21 and 21 respectively have approximately equal moments about pivot-pin connection B. By designing the slopes and contact points of surfaces 21b and 21a to produce forces F1 and F2 having thedirections shown, wear upon these surfaces caused by the tumbler lugs at the moment of engagement from the tumbler is equally distributed between the surfaces. This equal distribution of wear between the driving surfaces of each link and their corresponding tumbler lugs during braking becomes progressively more important as wear causes more of the links to make driving engagement with the tumbler lugs around the periphery of the tumbler, because the driving contact between the link flanges and tumbler lugs becomes more of a wiping contact and less of a striking contact when disengagement occurs nearer the top of the tumbler.

Turning now to Figure 10, this figure shows the invention assembled in a complete endless track unit, in which 71 and 72 are the upper rollers supporting the upper reaches of the endless track; '73, 74, 75 and 76 are the lower rollers supporting frame 77; 39 is the driving tumbler; and 78 is the idling tumbler. Upper rollers, lower rollers and the driving and idling tumblers all run in channel 22 of the links.

Having now described and illustrated one form of the invention, it should be understood that the invention is not to be limited to the specific form or arrangement of parts herein described and shown.

We claim:

1. A tread-belt link for a creeping-traction unit, said link having: a ground-engaging surface on the bottom thereof; a wheel-receiving channel on the top thereof; pivot means for connection with adjoining links, including a series of cars and recesses along the laterally-extending edges of the link and lateral pivot pins through said cars; a pair of upstanding wheel-guiding driving flanges, disposed laterally with respect to said channel on opposite sides thereof, disposed longitudinally in staggered relationship to each other, and having their outer lateral edges located adjacent opposite laterally-extending edges of the link; a pair of oppositely inclined lateral tumbler driving surfaces on each flange, the slope of the outer driving surface adjacent the lateral edge of the link being greater than the slope of the inner driving surface; and a tumbler bearing surface longitudinally aligned with each driving flange and extending longitudinally from an ear of the link across the body of the link, to the inner lateral edge of said flange, said surface being largely disposed on said body.

2. A tread-belt link for a creeping-traction unit, said link having: a ground-engaging surface on the bottom thereof; a wheel-receiving channel on the top thereof; pivot means for connection with adjoining links; a pair of upstanding wheel-guiding driving flanges, disposed laterally with respect to said channel on opposite sides thereof, disposed longitudinally in staggered relationship to each other, and having their outer lateral edges located respectively adjacent opposite laterally-extending edges of the link; and a tumbler-bearing surface longitudinally aligned with each driving flange, said surface being largely disposed on the body of the link.

3. A tread-belt link for a creeping-traction unit, said link having: a ground-engaging surface on the bottom thereof; a wheel-receiving channel on the top thereof pivot means for connection with adjoining links; a pair of upstanding wheel-guiding driving flanges, disposed laterally with respect to said channel on opposite sides thereof, disposed longitudinally in staggered relationship to each other, and having their outer lateral edges located adjacent opposite laterally-extending edges of the link; and a pair of oppositely-inclined lateral tumbler driving surfaces on the opposite lateral faces of each flange, the slopes of both surfaces being such that a line perpendicular to each surface at the point of driving contact with the tumbler passes through the body of the link adjacent to and inwardly of the opposite pivot-axis of the link, and the slope of the outer driving surface adjacent the lateral edge of the link being substantially greater than the slope of the inner driving surfaces.

4. A tread-belt link for a creeping traction unit, said link having: a ground-engaging surface on the bottom thereof; a wheel-receiving channel on the top thereof; pivot means for connection with adjoining links, including a series of cars and recesses along the laterally extending edges of the link; a pair of upstanding wheel-guiding driving flanges, disposed laterally with respect to said channel on opposite sides thereof, and disposed longitudinally in staggered relationship to each other; and a tumbler-bearing surface longitudinally aligned with each driving flange and extending longitudinally from the inner lateral edge of said flange on the body of the link, over said body, and thence on to an ear of the link, said surface being largely disposed on said body.

5. A tread-belt link for a creeping traction unit, said link having: a ground-engaging surface on the bottom thereof; a wheel-receiving channel on the top thereof; pivot means for connection with adjoining links, including a series of ears and recesses along the laterally-extending edges of the link; at least one upstanding wheel-guiding flange disposed laterally with respect to said channel, and having its outer lateral edge located adjacent one of the laterally-extending edges of the link; a longitudinally upwardly inclined lateral tumbler driving surface on each of the outer and inner lateral faces of said flange, the slope of the inner driving surface being less than the slope of the outer driving surface, and both slopes being such that a line perpendicular to each driving surface, at the point of driving contact with the tumbler, passes through the body of the link adjacent to and inwardly 'of the axis of the pivot-connection means on the opposite lateral edge of the link; and a tumbler-bearing surface longitudinally aligned with said driving flange and extending longitudinally from the inner edge of said flange, over said body of the link, on to an ear of the link, said surface being largely disposed on said body.

6. A tread-belt link for a creeping traction unit, said link having: a ground-engaging surface on the bottom thereof; a wheel-receiving channel on the top thereof; means for connection with adjoining links; an upstanding wheel-guiding flange, disposed laterally with respect to said channel; and a tumbler-bearing surface longitudinally aligned with said driving flange, said surface being .largely disposed on the body of the link.

unequally-inclined driving surfaces, pivot means for connecting adjoining links, and at least one tumbler-bearing surface laterally disposed with respect to the channel and longitudinally aligned with the driving flange and extending,longitudinally from a lateral edge of said flange on the body of the link, across said body, and thence to a lateral edge of the link, said surface being largely disposed on said body;and a driving tumbler having a series of peripherally-spaced laterally-projecting driving lugs, said lugs each having laterally-extending unequally-inclined driving surfaces adapted to make driving contact with thedriving flanges of the links, and said lugs each having a laterally-extending peripheral bearing surface to bear on the tumbler-bearing surface of the links.

8. A creeping traction unit according to claim 7, further characterizedby the fact that the lugs are associated in pairs, the lugs of each pair being longitudinally staggered and located one on each side of the tumbler; and that the slope of the outer inclined surfaces of each ,pair of said lugs is substantially less than the slope of the inner inclined surfaces of said pair.

9. A creeping traction-unit according to claim 8, fur- ;ther characterized by ,the fact that, when the outer inclined driving surface of a lug of the tumbler is in driving contact with a driving flange of a link, substantially all of the peripheral bearing surface of the lug is in contact with the tumbler-bearing surface associated with the longitudinally aligned flange of thesucceeding link.

10. A creeping traction unit according to claim 9, further characterized by the fact that the tumbler-bearing surface associated with each flange is approximately twice as long as the peripheral bearing surface of each lug of the tumbler, so that when a lug is in driving contact with a link flange, there is a gap between the rear inclined driving surface of said lugand the forward-inclined driving surface of the succeeding longitudinally aligned flange, said gap being approximately equal at the periphery of the tumbler to the peripheral length of the bearing surface of the lug.

11. A creeping traction unit according to. claim 7, further characterized by the fact that the lesser inclined driving surface of each flange has a greater convex curvature than the other driving surface of said flange.

12. A creeping traction unit according to claim 7, further characterized by the fact that the slopes of the driving surfaces of the link flanges and tumbler lugs are such that, when a pair of lugs are in full driving contact with the flanges of a link, the forces imposed by said lugs on such flanges have approximately equal moments about the forward pivot axis of said link.

References Cited in the file of this patent UNITED STATES PATENTS 2,385,923 Klaucke et al Oct. 2, 1945 2,452,921 Gillespie Nov. 2, 1948 2,530,379 Davidson Nov. 21, 1950 

